Collapsible boat formed from releasably connected laminar panels

ABSTRACT

A floating vessel comprising, in the orientation of use, a central longitudinal member ( 2 ) having a vertical height, and to each side of the longitudinal member an upper substantially laminar panel ( 3 ) connected to the longitudinal member and extending outwardly therefrom and a lower substantially laminar panel ( 4 ) connected to the longitudinal member at a distance below the upper panel and extending outwardly from the longitudinal member, wherein the outermost edges of the upper and lower panels are connected and the lower panel is larger in the outward direction than the upper panel such that the panels form a stable structure.

FIELD OF THE INVENTION

This invention relates to a floating vessel.

BACKGROUND TO THE INVENTION

Water sports are popular outdoor activities. In recent years new sportssuch as windsurfing and kite boarding are growing in popularity,compared to traditional sailing. They offer more fun and are moreaccessible in terms of money and space.

Mapping the practice of sailing around the targeted use of the boat, weobserve that new alternative water sports such as windsurfing and kitesurfing are getting more popular and are relatively less expensive thantraditional sailing.

On the other hand these alternative sports have higher access barriers,consisting of training time to learn how to windsurf and kite board.This is the major unique selling point of leisure boats such asrotomoulded catamarans (e.g. the Funboat manufactured by PerformanceSailcraft Europe Limited of Northamptonshire, UK, or the Bravo®manufactured by Hobie® of California, USA) which ensure higher stabilityand have easy boomless rigs.

Existing boats need to be transported on a trailer or the on top of acar. In this case it is difficult for one person to lift the boat overthe top (weight over 50 kg). On the other hand windsurf equipment can betransported on top of or in a car and one person can load and unload it.Furthermore windsurf equipment can be carried on the plane, while thatis impossible for boats.

Based on personal experience and informal exploration with sailors Ihave focused my attention on small recreational sailboats for oneperson. This segment represents an important slice of the boating marketand ranges from easy leisure boats to racing sail crafts. The commonneeds expressed by users during the early informal exploration areportability and easy of use. Hence the initial brief:

-   -   Sailing fun in a bag: “Create a new sailing experience that        enhances the fun of sailing given by the interactions with the        elements wind and water and that reduces the hassle associated        with assembling, transporting and storing the equipment.”

The open brief allowed me to investigate in the early stages new formsof sailing and generate hybrid concepts. The choice has been then for acraft that sails like a conventional dinghy but offers more portabilityand accessibility for new sailors. The project has focused on the boathull which is the real bulky part of the boat. Moreover, compatibilitywith existing collapsible sailing rigs, like the windsurf ones, lowersthe cost barrier for new users.

Nowadays the use of a foldable sailing boat responds to very specializedneeds. Most foldable boats are designed for fishing, kayak travelling oras emergency dinghies. Some of them have an optional sailing rig offeredby third parties. A new product needs to be placed in a wider scenarioof water and recreational outdoor sports.

Direct competitors are the very few collapsible sailing boats andfoldable kayaks with custom sailing rigs. Major examples of collapsiblesailing crafts are: the Aquaglide®, an inflatable multi-sport craftderiving from windsurfing manufactured by Aquaglide® of Washington, USA(retail price £350); the Stowaway® plywood sailing dinghy manufacturedby Stowaway® Boats Ltd of Northamptonshire, UK (£1,000-£2,000); and theTinker® inflatable with sailing kit manufactured by Henshaw InflatablesLtd of Somerset, UK (£2,500-3,000). Foldable kayaks are quite popularand their price range is £1,000-£2,500. Small companies offer customsailing kit for the most popular kayaks (£500-£1,000). The kit comprisesboat appendices because of the kayak's poor sailing performance. Themost common folding rowboats, mainly used for fishing or as emergencydinghies are probably the polypropylene Portabote® manufactured byPortabote®, California, US (from £1,300) and the aluminium Instaboat®manufactured by Instaboat®, Montmagny, Quebec, Canada (£800). For thefirst one there is now available an optional sail rig for £600. Finallyan entry level sport sailing dinghy has retail prices starting from£1,675 (the Topaz Taz®, manufactured by Topper® of Slough, UK), whilethe best-selling (the Laser® manufactured by Performance SailcraftEurope Limited of Northamptonshire, UK, with over 190,000 unitsworldwide) is £3,500.

The markets where collapsible sailing boat could compete are:

-   -   1. traditional sailing dinghies, by generating an affordable        entry level solution, which adds ease of transport and storage.    -   2. windsurfing, by sharing the same sails and making the switch        from one sport to another less expensive.    -   3. inflatables, by means of providing an easier and quicker        assembling system.    -   4. outdoor “week-end” sports and leisure activities such as        skiing, snowboarding, mountain biking, kayaking, thus winning        more enthusiasts to the boating sports.

SUMMARY OF THE INVENTION

This invention provides a floating vessel comprising, in the orientationof use, a central longitudinal member having a vertical height, and toeach side of the longitudinal member, an upper substantially laminarpanel connected to the longitudinal member and extending outwardlytherefrom and a lower substantially laminar panel connected to thelongitudinal member at a distance below the upper panel and extendingoutwardly from the longitudinal member, wherein the outermost edges ofthe upper and lower panels are connected and the lower panel is largerin the outward direction than the upper panel such that the panels forma stable structure.

It may be that the outermost edges of the panels are releasablyconnected. If they are then the panels are releasably connected to thelongitudinal member. It may also be that the panels are releasablyconnected with hook and loop fasteners.

It may be that the panels are formed of cellular or corrugated plasticsmaterial. If this is the case, then the corrugations or cells of theupper panel may run transversely to the corrugations or cells of thelower panels.

It may be that the longitudinal member comprises an aluminium beam.

It may be that the vessel is a boat.

BRIEF DESCRIPTION OF THE DRAWINGS

An embodiment of the invention will now be described, by way of exampleonly, and with reference to the accompanying drawings, in which:

FIG. 1 is a graph showing the righting behaviour of one embodiment ofthe invention at various angles of heel;

FIGS. 2 to 7 are pictures showing the process of packing one embodimentof the invention flat;

FIG. 8 is an illustration of polypropylene after profile rollingaccording to an embodiment of the invention;

FIG. 9 is a picture showing the fixing and sealing solution for theexternal edges of an embodiment of the invention;

FIGS. 10 to 15 are illustrations of the hull in use with various sails;

FIG. 16 is an exploded diagram of a hull according to one embodiment ofthe invention;

FIGS. 17 to 21 show a hull according to one embodiment of the inventionfrom various angles;

FIG. 22 shows a hull according to another embodiment of the invention;and

FIGS. 23 to 25 show three possible hull configurations according to theinvention.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

The proposed product is a small boat, designed for leisure sailing andcompatible with conventional sailing rigs (windsurf). The main featuresare the portability and the accessibility that aim to attract newenthusiasts to the boating sports. When needed, it folds to a flat packwith the dimension of windsurfing equipment.

From the industrial design point of view the key factor of this projectis the application of corrugated extruded polypropylene sheet to boatbuilding, using its properties to perform more functions. The foldedsheets are at once the boat skin and the structure; they form the livinghinges and generate embedded reserve safety buoyancy.

This product can be a first boat for young people, a leisure boat forfamilies, new sail enthusiasts. It can have a price range much lowerthan traditional boats and therefore comparable with other popularrecreational sport equipment such as high end mountain bike and or askiing set. To enter the target markets the strategy could be to offer aboat compatible with existing sailing rigs, thus lowering the pricebarrier to access for existing sailors and newcomers. This would alsolower the barrier regarding acceptability and feasibility, with thepossibility of partnering with existing known sail brands for deliveringcomplete boats over their distribution channels.

Product Specifications:

-   -   Crew: 1 adult person, average weight 75 kg    -   Sailing performance comparable to beginner sailing dinghies such        as Topper® Topaz Taz® or Laser® Pico®    -   Compact dimensions when folded for car transportation,        comparable with windsurfing equipment (Weight 25 Kg, Length 3 m,        “flat pack”)    -   Compatible with existing sailing rigs (e.g. windsurfing sails)

The boat is made out of a folded lightweight plastic sheet; e.g. sealedcorrugated extruded sheets, since they provide rigidity and highbuoyancy.

In the fold up configuration (sailing) it forms a hollow body, rigidenough to hold one passenger. In the closed position (transport) it is a‘flat pack’ of folded panels, which store inside the other parts(rudder, centreboard and sail rig).

The development of the concept has been carried out by dividing thedesign work in packages and reiterating the following design steps:

-   -   Hull design (shape the boat in the water)    -   Folding patterns (geometry studies to convert 2D in 3D)    -   Deck design (design the space for the crew)    -   Material and process    -   Detail design (fixing, sealing solutions)    -   Rig definition    -   Prototyping

Hull Design

The idea of folding flat panels to obtain the three-dimensional hullshape suggests that the boat is going to have a polygonal surface, a“mesh” of flat or curved faces. Several methods for generating hullshapes have been considered:

Wrapping: using a flexible sheet and bending or wrap it in order to finda stable configuration (fixed in the minimum number of points). Thismethod generates curved surfaces, but is quite hard to model onsoftware, because of the important role played by the materialelasticity. Thermoforming sheets has been used to sketch models.Meshing: starting with a traditional curved hull surface, is it possibleto mesh it on software packages to polygonal surfaces with small numberof faces. The difficult of controlling the mesh generator on the testedsoftware makes it difficult to obtain desired foldability and rigidity.Geometrical assembly: as the opposite of meshing, it is possible tobuild polygonal surface from scratch by adding polygons to simpleshapes. In this way it is possible to control the geometry and keepingthe foldability of the hull. 3D software packages allow to generatequickly many shapes, which have been easily visualised with papermodels.

With the last method a classification of possible polygonal surfaces,according to simple parameters as number of sides on the plan and on themain section. By increasing the number of sides the hull comes closer tothe traditional curved hull, thus improving the performance but makingthe folding and structural issues more complex.

The hull shapes have to satisfy basic parameters to be considered for aboat. With the help of naval architecture texts and experts, I compileda list of the primary criteria to analyze a sailing vessel:

Structural rigidity: especially longitudinal rigidity. The boat must notbend due to the effect of compression between water and crew weight.Buoyancy: besides keeping afloat the crew without drafting too much, theboat needs to have reserve buoyancy for safety reasons. Positiveflotation is the property of floating when filled with water (e.g. aftercapsize), and is normally achieved with extra floating bodies (e.g.foam) attached to the boat.Stability: especially transversal stability is important for sail boats.The boat needs to generate a righting moment when heeled on the side.For small dinghies without a keel, this is anyway not enough towithstand the force of the wind on the sail and the position of the crewis crucial to keep the boat upright. Nevertheless stability is alsocomfort: not heeling hull design excessively when the crew moves fromcentre to side, is also much appreciated.Drag: the resistance to the motion in the water is mainly given by thefriction of the water on the boat, and it is proportional to the wettedsurface. The second main component is generated by the motion of thewaves.Plane: the capacity of the boat to generate a vertical lift by the flowof the water under the hull depends on the hull geometry. If so the boatrises from water at speed (plane) and reduces the resistance to motion.This hydrodynamic effect is quite complicated to calculate also withsoftware and is generally tested in water with models. Generally theflatter the hull, the more the lift it generates.“Sailability”: or behaviour of the vessel in the sea in differentconditions; e.g. sea-worthiness and sea-kindness.

The first four criteria can be predicted with calculations based on thehull geometry and have been analyzed for the generated hull shapes. Aprofessional software (Rhinomarine, a 3D CAD/CAM program for modellingboats, their hydrostatics, stability and performance, produced byProteus Engineering) has been used for the calculations. They do notexclude any of the shapes nor do they give us a clear winner. Theyconfirm the intuition that increasing the number of sides, theperformances increase as we have more parameters to adjust. The choiceof the shape is then a trade-off between hull design and the otherdesign areas, where these naval architecture criteria have also beenconsidered.

The hydrostatic parameters for the proposed design have been alsocalculated and following these results, we can make followingconsiderations.

Structural rigidity: The boat is designed for a displacement of 125 kg,i.e. the weight of a person (75 kg) plus the boat and eventualequipment. The pressure on the hull is therefore 125 kg over the wettedsurface (about 2 m²), which in different sailing conditions may reduceup to 50% (boat on a wave or on the plane): therefore 125 Kg/m².

Buoyancy: The twin-walled plastic sheet is extremely buoyant and givesthe boat an embedded safety reserve buoyancy, able to hold a personafloat in the case the boat should open up in water. The boat is made ofabout 10 m² of empty sheet: with an average thickness of 6 mm weight of1 kg/m², the material accounts for a positive flotation of 50 kg, enoughto hold the equipment (mast) and support the person afloat. When foldedup, the boat generates an enclosed volume of about 300 litres, whichgives an displacement for 300 kg, useful for safe navigation on waves,when water may fill up the deck.

Stability: As can be seen in FIG. 1, the boat has a positive rightingmoment (i.e. tends to return upright) up to a heel angle of around 80degrees. The curve is calculated for an initial draft of 10 cm and aweight of 100 kg (in the middle of the boat).

Folding Patterns

Since the first paper models it has been clear that the folding plays animportant role for the structural strength. A constant rule for thegeneration of folds, has been the utilization of triangular faces, inorder to create only volumes composed by a number of tetrahedrons, tomaximize the structural stability of the shape and to not rely only onthe rigidity of the material. This approach guides the choice of thehull shape towards those with the least number of sides. The chosenshape is composed of two symmetrical tetrahedrons joint in the middle.More complicated shapes require dividing up the volume into moretetrahedrons and requiring more material, which then has to fold to aflat pack of minimal dimension.

In order to maximize the longitudinal rigidity no bends have been madeon the longitudinal dimension. The boats folds up as a book with thespine on the length.

Important structural element of the boat is the transom. Different arethe possibilities offered by the fold:

Double bottom: elegant and efficient solution that resist the folding inorder to achieve necessary rigidity and sealing.Solid transom (inserted panel): easy and structurally sound solution,adds an extra part to be carried and stored in the boat.Solid transom (folded up): the sheet folds on the back as they fold onthe front. This is the solution chosen for the proposed design.

Deck Design

After the water test of the test rig the deck has been redesigned. Thecrew on a sailing boat has to change position quite often and be able,especially on small dinghies, to sit anywhere in order to balance theboat. While a flat and slightly concave deck is actually quiteappropriate for the latter purpose, it is quite uncomfortable for thelegs, forcing the person to kneel rather than sit.

A raised border on the sides has been added to the final design in orderto allow the passenger to sit on it. The border is an additional smalltetrahedron with many functions. Besides forming a seat for the crew andsomething to hold on, it adds rigidity to the side. Most importantfunction it joins the two sheets and forms the sealing.

Compared to the test rig configuration, the final design has two sheetsof corrugated plastic, fixed in the middle to the central frame.

This configuration besides allowing the raised side border, allows alsoto use material of different thicknesses and to orient the corrugationsof the two sheets in different directions, to increase the stability.

FIGS. 2 to 7 show the chosen folding pattern. FIG. 2 shows the boatready for use. To pack the boat away the user must open the sides (FIG.3), open the back (FIG. 4), insert the spars and close the internalsheet (FIG. 5), close the external sheet (FIG. 6) and pack the boat flat(FIG. 6).

Material and Process

Materials suitable for this application are:

-   -   Multi-walled extruded polypropylene sheets, such as those used        for signs, packaging or construction. For example, Correx® is a        product produced by Kaysersberg® Plastics of Kaysersberg,        France. Similarly Corriboard® is a product produced by Northern        Ireland Plastics Ltd, Country Down, Northern Ireland. Corrugated        polycarbonate sheets, which are available in a wider range of        thicknesses and rigidity and often used for clear roofing.    -   Plain polypropylene sheets    -   Woven polypropylene sheets such as CURV®, which is produced by        Propex Fabrics® GmbH Gronau, Germany    -   Aluminium sheets joined with rubber or neoprene hinges

The choice of Correx® has been guided by the idea of realizing manyfunctions in one part. The sheets act as the skin of the boat, havestructural properties given by the rigidity of the corrugation, work asliving hinges and when sealed on the edges they assure an extrabuoyancy, very useful for a boat. With any other solution an additionalmaterial should have been introduced to realize those functions: i.e. afoam insert on the plain sheets to increase buoyancy.

Correx® is commercially available with a thickness range from 2 mm to 10mm, with different grades. The test rig has been made out of 10 mmtwin-walled polycarbonate sheet, proving to be rigid enough. The twosheets included in the proposed design can have different thicknesses,the internal one being lighter. Rigidity depends mostly on the thicknessof the single layers or walls of the sheet profile. The right choice hasto be made after building full scale prototypes with sheets in the 6 mmto 10 mm range.

The availability and the price on the market of this material is one ofits advantages.

If the boat would be produced on a large scale, it might be possible todevelop a custom extrusion. In that case the external layer should bethicker to increase the resistance to abrasion, the cells should have atriangular profile, which increases stability and makes scoring thefolding lines easier.

Different solutions have been investigated to create the folding lines.The choice has fallen to profile rolling because it does not requirebonding of material to polypropylene, which is possible only throughwelding (no adhesive are available for polypropylene) and thereforedifficult for large surfaces. FIG. 8 illustrates the appearance ofpolypropylene after profile rolling.

To score the folding lines on the corrugated sheets, different tools andcombinations of process parameters have been tested (i.e. temperature ofmaterial and tool, pressure and speed). The most successful process hasbeen realized with a custom made tool that resembles an industrialpizza-cutter and prototypes a manual profile rolling. The material hasbeen heated close to melting temperature and a cold tool has achievedbetter surface finishes.

Profile rolling allows furthermore to create curved hinges. These arequite important aesthetic features for the final design, as well as theyallow the creation of curved surfaces.

Detail Design

The central frame has been introduced to add longitudinal rigidity tothe boat and provide a structural element where all the equipment can befixed: mast, centreboard, rudder, mainsheet and foot straps for thecrew.

Materials that have been considered are: injection mould, pultrusion,aluminium extrusion, PVC extrusion, composite and fibreglass (GRP).

While the injection mould tends to be too expensive and technicallydifficult for this length, the pultrusion does not work well in torsion.The PVC extrusion has been used for the test rig and had to bereinforced to achieve sufficient rigidity. Aluminium extrusions can berealised in custom profiles, which would allow a better fixing of theCorrex® sheets. It would be realised as the aluminium spars, which arethe most common material for actual sailing masts.

The edges of the external Correx® sheet are welded at the bow and stern,in order to realize a closed surface in contact with the water. Externaland internal sheet are fixed to the central frame. The external edges ofthe two sheets fold on themselves realizing the seal to water, whenrubber sealing strips are provided on the contact surfaces.

Several possibilities have been considered for the fixing of the fold:buttons, straps, bolts and Velcro® (hook and loop fastener). The lastpossibility has many benefits: lightweight, easy to open and close,invisible. Industrial types of Velcro® are available with high strength.Especially the moulded tapes, with symmetrical “mushrooms” sides. Theseplastic tapes can be glued or better welded to the polypropylene sheets.The symmetric tapes can used both for fixing the boat in the fold upconfiguration as well as flat pack.

An alternative to seal solution is an inflatable chamber inside theenclosed volume between the sheets. Such a chamber, realized in thinelastic material which folds on one of the sheets when closed, wouldsolve completely the sealing problem, occupying the volume with air andgiving extra rigidity to the structure. This solution has not beenintegrated so far to simplify the assembly process for the user andavoid pumping.

FIG. 9 shows the fixing and sealing solution for the external edges.

Rig Design

The design of a foldable sailing rig was included in the initial conceptand different configurations have been considered. On the other side,masts in sections are quite collapsible and I decided to focus on thehull, which is the real volume to collapse, as the result of thisproject.

On the other hand, the idea of fitting commercially available rigs fromother boats and especially from windsurfs has many benefits:

Wider range: windsurf sails are available in wide range of sizes tomatch the wind conditions. Similar concept could fit this lightweightboat.Weight: windsurf rigs are lighter, because using fibre masts and that isessential for this lightweight boat.Business model: attractive commercial strategy to enter the market withlower barrier: entry level customers do not need to buy a sail, but canreuse old ones. Windsurfers can have a low cost switch to sailing for aday or for the family. Custom sail could always be offered as optional.

FIGS. 10 to 15 show the hull in use with various sails: FIG. 10 is awindsurf like rig (boomless), for example a ‘batwing’ sail for a kayak;FIG. 11 is a rigid wing (more efficient, smaller size); FIG. 12 is atraditional mast/boom rig, for example a Topper; FIG. 13 is a Lateensail (boomless) with front mast supports; FIG. 14 is a Lateen sail(boomless) with back mast supports; and FIG. 15 is a foldable rigid sail(in sections), same material as the hull.

Prototyping

During the whole process models and prototypes have been used:

Paper modelsPolypropylene and Correx® scale models: to test the folds with thickerand harder material and to test in water.RC model: the first sailing of the proposed hull shape has been realizedwith a radio controlled model with a polypropylene hull in scale 1:5.Full-size cardboard model: The model has been used as test rig for thefolding/unfolding process. The model showed how easy the folding couldbe and give an idea of the handling of boat in real size. Focusing onthe fixing, this prototype inspired the idea of welding together thesheet edges at bow and stern; so that they are automatically in placeduring the opening/closing process. The idea of embedded handles foreasy transportation came also from this test rig.Full-size sailing test rig: It is made out of separate corrugatedpolycarbonate roofing sheets. The frame is obtained welding PVC squaretubes and the hinges are realised with PVC tubes fixed to the sheetswith fibreglass reinforced tape and hinged on an aluminium rod. Thesailing rig and equipment is borrowed from a Topper dinghy and theweight of the mast has forced us to use a metal reinforcement on the PVCframe. The sealing has been obtained by taping the hinges, thuspartially restricting the unfolding process. The total weight of theboat is 27 kg.

Features introduced during prototyping are: Improved deck design withraised borders; Velcro® fasteners; curved hinges; two corrugated sheetswith corrugation in different direction for added rigidity.

Proposed Design

Dimensions:

-   -   fold up: 2.8 m×1.55 m×0.35 m    -   flat pack: 2.98 m×0.90 m×0.10 m    -   weight: 25 kg

Twin-wall extruded polypropylene sheet is used, cut and scored (profilerolling) to form the folding lines. Edge sealing and welding thematerial weights 15 kg and the required quantity (10 m²) costs on themarket about £60.

The frame is aluminium extrusion Machined to realise the fitting to theother parts. The supports (mast, centreboard, rudder) are injectionmoulded parts. The fasteners are industrial moulded “Velcro®” tape(welded on the polypropylene sheets) supports internal sheet framesealing and fasteners external sheet

FIG. 16 shows the design, which is composed of an external sheet ofmultiwall extruded polypropylene 1, an aluminium frame 2, an internalsheet of multiwall extruded polypropylene 3, a nylon injection mouldedmast support 4, nylon injection moulded centreboard supports 5, 6, anylon injection moulded rudder support 7 and rubber and Velcro® sealingstripes 8,9.

FIGS. 17 to 21 show a completed hull from various angles. FIG. 22 isanother illustration of a completed hull. FIGS. 23 to 25 are threepossible two-sheet configurations of the hull.

1. A floating vessel comprising, in the orientation of use, a centrallongitudinal member having a vertical height, and to each side of thelongitudinal member, an upper substantially laminar panel connected tothe longitudinal member and extending outwardly therefrom and a lowersubstantially laminar panel connected to the longitudinal member at adistance below the upper panel and extending outwardly from thelongitudinal member, wherein the outermost edges of the upper and lowerpanels are connected and the lower panel is larger in the outwarddirection than the upper panel such that the panels form a stablestructure.
 2. A floating vessel as claimed in claim 1, wherein theoutermost edges of the panels are releasably connected.
 3. A floatingvessel as claimed in claim 1, wherein the panels are releasablyconnected to the longitudinal member.
 4. A floating vessel as claimed inclaim 2, wherein the panels are releasably connected with hook and loopfasteners.
 5. A floating vessel as claimed in claim 1, wherein thepanels are formed of cellular or corrugated plastics material.
 6. Afloating vessel as claimed in claim 5, wherein the corrugations or cellsof the upper panel run transversely to the corrugations or cells of thelower panels.
 7. A floating vessel as claimed in claim 1, wherein thelongitudinal member comprises an aluminium beam.
 8. A floating vessel asclaimed in claim 1, wherein the vessel is a boat.
 9. (canceled)